It is the objective of the present invention to achieve highly sufficient removal of ammonia from fabric by the use of water as a medium of heat exchange with a much lower temperature range than heretofore thought possible. The invention concerns a new and thermally unique technique for removing ammonia from fabric after treatment in a liquid ammonia bath. In accordance with previously known technology, after fabric is immersed in the liquid ammonia bath, it is squeezed free of excess ammonia by padder rolls which reduce the retained amount of ammonia to about 70% ammonia by weight of fabric. The remainder is then removed by passing the fabric through a palmer (dryer) to dry the fabric completely. The by-product of this drying step is aqueous ammonia for which a commercially feasible market must be found. Ammonia removed from the liquid ammonia treatment process due to its entrapment in the fabric and subsequent removal as described, must be replenished at more expense than can be recouped by the sale of the aqueous ammonia by product. The total energy cost for the removal of liquid ammonia in this conventional process has been calculated to be about 460 BTU's per pound of ammonia removed from fabric, where the fabric is a denim.
It has been proposed to remove ammonia from fabric subsequent to the liquid ammonia treatment by subjecting the fabric to a hot water bath only slightly below the boiling point of water, say at about 210.degree. F. However, the thermal economics of treating fabric at such a temperature are not encouraging since it has been calculated that approximately 8500 BTU's must be expended in order to remove one pound of ammonia from fabric. Also, since the vapor pressure of water at this temperature is quite high, a great deal of water will accompany the ammonia being vaporized from the fabric, presenting a severe problem to recover the ammonia constituent, and requiring substantial amounts of energy to maintain the temperature of the bath (every pound of water vaporized at approximately 210.degree. F. requires about 970 BTU's ).